Filament spinning apparatus



June 11, 1968 w iv -r'r, JR" ET Al. 3,387,327

FILAMENT SPINNING APPARATUS Filed June 9, 1966 6 mw 2 m O 2 a u 5. W -l-6 w m I m I H 3 m in a M i K 7 w. B m H I 9 L I .4 F a m m 8 5 7" 2 e ma I F F 2 United States Patent 3,387,327 FILAMENT SiINNlNG APEARATUSWilbur J. Privott, .lr., Raleigh, and Rodney M. Chapman, Kinston, N.C.,assignors to Monsanto Company, St. Louis, M0., a corporation of DelawareFiled June 9, 1966, Ser. No. 556,476 3 Claims. (Cl. 18-8) ABSTRACT QFTHE DISCLOSURE In this invention, a spinnerette produces a self-crimpingfilament from a source of a thermoplastic filament-forming material byadmitting to an extrusion orifice at least two streams of differentcross-sectional areas but substantially equal mass fiow rates to form amono-conjugated filament having, upon the stretching thereof,substantially different degrees of orientation across its cross-section.

This invention relates to an apparatus for producing synthetic textilefibers, and more particularly, to an improved spinnerette constructionfor the production of selfcrimping synthetic filaments and fibers.

Various embodiments of apparatus for producing selfcrimping compositesynthetic filaments from two or more discrete and usually spinablemediums capable of forming filaments upon evaporation, coagulation orcooling are described in the prior art. However, such apparatus arehandicapped by certain disadvantages, particularly as regardsintricacies of construction and limitations on uniformity of product,which have limited their commercial utilization.

Typical of the prior art spinning apparatus employed to produceself-crimping bicomponent filaments are those wherein at least twodiscrete systems of fluid passageways interconnect two discrete sourcesof polymeric fiber-forming material with each spinning orifice, thedistinct sources of material being maintained separate throughout thefilament forming process until a point of merger is reached at or inclose proximity to the extrusion orifice, wherein the spinning materialsare united, normally in a side-byside or sheath/ core arrangement, intoa unitary filament having a uniform cross-sectional distribution of thecomponents throughout the length of each filament. By such a techniqueof pairing at least two disparate fiber-forming materials to form asingle filament, such filament may be caused to possess a crimpingpotential upon suitable aftertreatment due to a differential in physicalproperties between the components, especially as regards shrinkage and/or elastic recovery. A primary detriment suffered by such a techniqueresides in the necessity of providing separate melt sources and pumpmechanisms with the attendant problem of maintaining the desiredinto-control between the separate systems. Also, such an approach relieson the inherent disparities and physical properties of the twofiber-forming mediums employed and, in many instances, it has been foundmost difficult, if not impossible, to accommodate the pecularities ofeach melt in a conjugate spinning system, particularly as regardsoptimum melt and extrusion temperatures and gell rates, in the case ofmelt spinning.

A somewhat different approach to obtain a filament of self-crimpingpotential utilizes essentially only a single source of fiber-formingmaterial which is conveyed as separate streams of differing thermalhistory (particularly as regards time and temperature) to therebyestablish a disparity in those physical properties found to beproductive of self-crimping capability. Another proposal for obtaining afilament of self-crimping potential does not rely on the merger of twoor, more streams of material having, or which are caused to have,disparate physical properties,

3,387,327 Patented June 11, 1968 ice but is essentially no more thanconventional mono-component spinning accompanied by asymmetricalquenching to establish an asymmetric differential in birefringence overthe filament cross section. Each of these approaches has been recognizedto have shortcomings as regards uniformity of treatment and consequentuniformity of crimp formation, as well as being limited in their abilityto produce filaments having a sufiiciently high crimp capability formany applications.

In light of the foregoing problems and recognized shortcomings itbecomes an object of the present invention to provide a spinningapparatus capable of producing filaments having self-crimpingproperties, each of which filaments is formed from the merger of two ormore streams which may, though not necessarily, be of identicalcomposition, thermal history and quench treatment. A further object ofthis invention is to provide a spinning apparatus capable of producing aplurality of such selfcrimping filaments having a uniform cross sectionthroughout their lengths and, in the preferred embodiment, having anequality of distribution of components formed from each of the severalstreams merged to form a given filament. Still another object of theinvention is the provision of an improved spinnerette construction bywhich self-crimping synthetic filaments may be produced from a commonsource of polymeric fiber-forming material. Another object is theprovision of a spinnerette construction for the production ofself-crimping synthetic fibers, which construction involves only minormodifications of an otherwise conventional mono-component spinningsystem.

In accordance with the present invention, the foregoing and otherobjects are attained by providing, in a synthetic filament spinningsystem, an improved spinnerette construction characterized by at leastone pair of converging passageways or orifice capillaries wherein theexit regions of such capillaries are of differing cross-sectional areas,whereby the fiber-forming medium passing through each of the capillariesis caused to issue into a common filamentary stream at different linearvelocities. The differential in linear velocities of the constituentstreams forming a given filament established by such a spinneretteconstruction results in a filament possessing an asymmetric differentialin orientation when the filament, so extruded, is withdrawn from theorifice at a linear velocity exceeding that of any constituent stream.Upon drawing and/ or optional heat relaxation, such an asymmetricdifferential in orientation over the filament cross section becomesmanifest by a contortion of the thentofore straight filament into ahelically crimped configuration of readily controlled frequency andamplitude. Such a self-crimping capability has been viewed as arisingfrom a differential in elastic recovery after drawing and/ or adifferential in shrinkage upon, for example, heat relaxation, resultingin the generation of an imbalanced system of forces acting over thefilament cross section to contort same into its crimped configuration.Whether by the mechanism of elastic recovery or shrinkage, thedifferential in response to the release of drawing tension or exposureto heat relaxation has been ascribed to the asymmetric differential inorientation over the filamentary cross section. In any event, it isamong the objectives of the present invention to provide a novel andsimplified means of effecting such a differential orientation.

The differential in jet-stretch to which a filament may be subjected byextrusion through the subject apparatus has a prime advantage in theability to produce a selfcrimping filamentary structure from a commonmelt source, which source may, in the preferred mode, be conveyed to thespinnerette itself as a single stream, at which point it is momentarilysub-divided through two or more discrete groups of capillaries ofdiffering cross-sectional exit areas, each of which groups ofcapillaries may comprise a plurality of individual capillaries supplyinga plurality of orifices, hence merging two or more capillary streamsfrom two or more of such groups of capillaries into a single streamhaving a differential in linear velocity over its cross section. It isto be recognized, however, that the concept of extruding constituentstreams at a differential in linear velocity to form a unitary filamentmay advantageously be practiced in conjunction with conventionalbicomponent spinning techniques and apparatus; for example, twochemically and/ or physically disparate fiber-forming mediums, by virtueof the inter-relationship of certain of their chemical and/ or physicalproperties, may be combined into a unitary filament having aselfcrimping potential, which potential may be enhanced or modified bymerging such disparate melts at differential linear velocities.

Also, though the following discussion shall be largely in terms of aside-by-side merger of constituent streams to form a unitary filament,the concepts herein disclosed may be as well practiced in the form of asheath/core merger, wherein a core stream is injected into a sheathstream having a different velocity, with extrusion into a unitaryfilament occurring proximate to the point of such sheath/ core merger.Similarly, a great variety of orifice cross-sectional configurations mayas well be employed in utilization of the present spinning apparatus toproduce self-crimping filaments having a wide variation incrosssectional configuration.

The juncture of the orifice capillaries supplying a given orificepreferably meet substantially coincident with their points of exit atthe downstream surface of the spinnerette plate, but it will be clear tothose skilled in the art that such juncture may occur either somewhatprior to issuance through the orifice or somewhat downstream of thepoint of exit from the spinnerette face, the essential limitation beingthat two or more appropriate capillary streams may ultimately be causedto unite into a single unitary filament prior to substantialsolidification, else separation of the constituent streams may bedifficult or impossible to avoid. Also, the angle of convergence of thetwo or more capillaries forming a given filamentary stream has not beenfound critical to the extent that merger is not so abrupt as to generateturbulent flow and the consequent possibility of unduly blending theconstituent streams. It is, however, contemplated that controlled amountof blending of the constituent streams may be desired in certaincircumstances; viz, where it is found that component separation is aproblem, such a blending of the interface between two or moreconstituent streams has been found to provide improved resistance toseparation tendencies during further processing.

For a better understanding of the constructional details of thespinnerette apparatus constituting the present invention, reference isnow had to the accompanying drawings as illustrating typical embodimentsthereof and in which:

FIG. 1 is an axial cross section of one arrangement of the spinneretteassembly showing the alignment of the spinnerette capillaries, orificesand spinnerette pack assembly, which arrangement is particularly adaptedto handling two disparate fiber-forming mediums, but is not limitedthereto;

FIG. 2 is a plan view of the spinnerette interface taken along line 22of FIG. 1 and showing pairs of large and small orifice capillariesarranged in a concentric circle pattern;

FIG. 3 is a plan view of the outer or orifice face of the spinnerettetaken along line 33 of FIG. 1 showing the preferred concentricarrangement of spinnerette orifices;

FIG. 4 is an enlarged fragmentary cross-sectional view of anotherembodiment of the spinnerette capillaries and orifices shaped to embodythe concepts of this invention;

FIG. 5 is an enlarged fragmentary View of still another form ofspinnerette capillaries and orifices according to this invention; and

FIG. 6 is an enlarged fragmentary cross-sectional view of a thirdembodiment of spinnerette capillaries and orifices configured accordingto the teachings herein.

Referring now to FIG. 1, there is shown in the assembled cross-sectionalview a spinnerette assembly comprising a spinnerette pack 11 and aspinnerette plate 1 mounted in face-to-face relationship wherebyappropriate passages within the pack and plate are placed in register todefine continuous passageways throughout the assembly. Considering firstthe details of the spinnerette plate 1, as further illustrated in FIGS.2 and 3, the plate may take the form of a circular disc havingsubstantially parallel surfaces, viz, the upper or interface surface 5and the lower or orifice surface 15. A plurality of pairs of capillaries2 and 3 are provided in the spinnerette plate wherein capillary 2 isprovided with a larger cross-sectional area in the vicinity of orifice16 relative to that of capillary 3. In the embodiments illustrated,capillaries 2 and 3 are located in concentric circles, but virtually anyother desired arrangement may be as well accommodated as, for example,chord-wise extending rows of orifices. The capillaries communicatingwith a given orifice are preferably formed in the spinnerette plate atan angle such that the capillary path lengths are substantially equal,both capillaries emanating from the orifice face of the plate 15tangentially as a common conjugate orifice 16, as depicted in FIGS. 1and 3.

An essential feature of this invention resides in the relationshipbetween the cross-sectional areas of capillaries 2 and 3 in the vicinityof the orifice, which relationship is such as to impart a differentiallinear velocity in the constituent streams issuing from such orificewhich, upon taking the resulting filament up at a linear speed exceedingthat of any constituent stream, results in imparting an asymmetricdifferential orientation due to the differential jet-stretch thusimparted to the filament. As previously mentioned, the result is afilament having a differential response to either or both the release ofa drawing tension, resulting in a spontaneous crimp formation, and adifferential shrinkage in response to such as heat relaxation.

In accordance with our invention, it therefore follows that, to achieveself-crimping unitary filaments which, for purposes of illustration,contain no inherent disparity of properties such as may normally resultin self-crimping capability, the ratio of the cross-sectional area ofcapillary 2 in the orifice region to that of capillary 3 must be greaterthan 1. That is A /A 1 Where A =cross-sectional area of larger diametercapillary 2, A =cross-sectional area of the smaller diameter capillary3.

Where it is desired to produce filaments exhibiting an equality incomponent distribution (viz, assuming an orifice supplied by twocapillaries, the resulting bicomponent filament would exhibit a 50:50contribution of the constituent streams from each capillary), the flowrate through each capillary supplying a given orifice must equal that ofthe constituent flows. This may be accomplished by several techniques,all of which function to provide an increase in the flow resistance ofthe larger capillary to insure an equalization of the mass flow ratewith that of the smaller capillary.

For example, in the embodiment illustrated in FIGS. 1-3, such anequality in resistance to flow is accommodated in the spinnerette pack11, as best depicted in FIG. 1. As there shown, spinnerette pack 11consists of a circular disc having two annular passageways 13 and 14interconnected to a polymer source 12, which may be in the form of twodiscrete fluid-forming mediums, or a single such medium (in the formercase, one source would supply annular passageway 13 and the other sourcewould supply passageway 14). Assuming a common source, the supply 12 isconveniently forwarded from a conventional spinning source through aconventional gear-type meter pump, neither of which are illustrated.

Annular passageways 13 and 14 divide the single polymer stream into apair of streams, each of which in turn supply a plurality of capillaries2 and 3. A filter screen 9 is provided in passageway 13 through whichthe polymer flows into distribution passageway 4, which latter serves tofeed the plurality of smaller cross-sectional area capillaries 3.Annular passageway 14 has disposed therein a fine mesh screen 7superposed by a small amount of size A sand granules, and two additionalscreens 8 overlying the granules. The screens and sand provide the addedresistance to flow required to insure substantial equality in the massflow rates between each of that group of capillaries supplying a givenorifice. The polymer flows through the filter pack into distributionpassageway 5 which supplies the plurality of larger cross-sectional areacapillaries 2.

The polymer flowing through the aforementioned spinnerette pack 11 andspinerette 1 is thus divided into two separate groups of streams, eachof which is extruded through a plurality of capillary 2 or 3, whereinthe linear velocity of the stream passing through capillary 3 is causedto be greater than that passing through larger capillary 2. The polymerstreams are caused to combine into a unitary filament in a side-by-siderelationship in the vicinity of orifice 16. Subsequent to the extrusionand formation of the filaments, they are drawn away at a higher linearvelocity than that of either constituent stream as such streams emanatefrom orifice 16.

It is to be understood that the embodiment illustrated in-FIGS. 1-3 donot require utilization of the spinnerette pack 11 illustrated unless itis desired to process filaments from two discrete melt sources;otherwise, a common melt source may be passed directly through each ofthe capillaries supplying a given orifice, suitable provision being madefor equality in flow resistance of the capillaries where it is desiredto produce a filament exhibiting an equality of component distribution.

It will readily be appreciated that the various embodiments of thepresent construction may be sized to accommodate a wide variation inboth linear jet velocity ratio and mass flow rate ratio to providefilaments exhibiting a great variety in jet stretch differential and/ormass ratio of the constituent streams forming a given filament byvarying the size and configuration of the capillaries supplying a givenorifice according to well known principles of fluid mechanics.

Referring to FIG. 4 of the drawings, in which another embodiment of theinvention is shown, reference numeral 17 indicates the spinnerette platewherein capillaries 20 and 21 are shaped to have differentcross-sectional areas and to terminate in a common orifice 22 in thelower spinnerette face 19. Cavities 23 and 24 are provided in the upperface 16 of the spinnerette, both be'ng formed to substantially the samedepth to achieve substantially equal length capillaries 20 and 21.Within cavity 24 there is provided a resistance element 25, which mayconsist of a plurality of screens, sand granules, sintered metal filterelements or the like, such that substantially equal mass flow rates areestablished in each capillary supplying a given orifice.

Referring to FIG. 5 of the drawings, in which yet another embodiment ofthe invention is depicted, reference numeral 26 denotes the spinneretteplate through which an enlarged cross section is taken. Formed in thespinnerette are capillaries 29 and having tapered bores. Capillary 29 isformed in the spinnerette plate from face 27 and makes an angletherewith, while capillary 30 is formed therein from face 28 to makesubstantially the same angle as that of capillary 29 to provide equallength capillaries and substantially equal bores for both capillaries atthe respect faces 27 and 28. Such a capillary configuration provides forsubstantially equal mass flow rates through each capillary and thecombined streams emanating from orifice 32 will have differentinstantaneous linear velocities due to the difference in thecross-sectional areas between the capillaries at their termination insurface 28 of the spinnerette plate.

Referring to FIG. 6 of the drawings, in which still another embodimentof the invention is depicted, reference numeral 33 represents thespinnerette plate through which an enlarged cross section is taken.Disposed in the spinnerette plate are capillaries 36, 37, 38 and 39 withcapillaries 36, 39, and 37, 38 having equal cross-sectional areas. Thepath length of capillaries 36, 39 and 37, 38 are such that there will besubstantially equal mass flow rates through each with the fluid streamsemanating from capillaries 37, 38 having a higher linear velocity thanthat of the fluid streams emanating from capillaries 36, 39.

The spinnerette plates depicted in FIGS. 4, 5 and 6 are of suchconstruction that a conventional spinnerette pack may be used therewithin lieu of the pack depicted in FIG. 1 in that the restrictive flowmeans is incorporated directly within the spinnerette construction perse.

Utilizing the aforementioned apparatus, the production of self-crimpingfibers consisting solely of a single polymer is afforded through themechanism of differential jetstretch, wherein extrusion of a singlepolymer is accomplished through two or more converging and unequal areacapillaries to impart unequal linear velocities to the streams passingtherethrough and the resultant unitary filaments are taken up at agreater linear velocity than that of any constituent stream emanatingfrom a given orifice. The freshly formed filaments are differentiallyjet-stretched as they issue from their orifices and prior tosolidification, with that portion of each filament having the lowerlinear velocity receiving the greater jetstretch. This treatment impartsto the constituent zones of the unitary filament different crystallineand shrinkage characteristics which results in the formation of ahelical crimp in the filament upon their being relaxed after drawing,optionally followed by inducement of differential shrinkage. Normally,the side of the filament having the higher degree of jet-stretch has thehigher percent shrinkage after drawing and is seen to form the inside ofthe helix of the crimped filaments.

The following example illustrates the use of the apparatus of theinvention for the production of permanently crimped filaments which maybe formed from polymers of polyethylene terephthalate, polyamide,polyacrylonitrile, polyolefin, polypropylene and the like, as well asblends thereof.

Example A differential jet-stretch spinnerette and spinnerette pack asdepicted in FIG. 1 was placed in the meter pump block of a conventionalmono-component melt-spinning machine. Spinnerette plate 1 .had formedtherein converging pairs of capillaries having 0.062 inch and 0.031 inchdiameters. The spinnerette pack 11 contained in passageway 13 two 60mesh screens 9 which provided filtration media for the fluid streamfeeding the smaller diameter capillaries 3; passageway 14 contained one200 mesh screen 7, approximately oneg ram of size A sand granules 10,and two 60 mesh screens 8 which provided a restricted flow path for thefluid stream passing through the larger diameter capillaries 2.

' Polyethylene terephthalate polymer having a specific viscosity (1 of0.40 as determined with 5 grams of polyethylene terephthalate, per ml.of solvent consisting of a 2:1 weight mixture of phenol/trichlorophenolat 25 C.

The polymer was melted and extruded at .a melt temperature of 275 0.,into filaments through the aforementioned spinnerette pack and plate bymeans of a single meter pump at a pumping rate of 2.5 cc./minr Thefollowing conditions were maintained during spinning:

The freshly spun and quenched filaments had a differential jet-stretchratio of approximately 4:1 and were taken up as a unified bundle on aconventional take-up assembly. The filament bundle was subsequentlycolddrawn at a draw ratio of 4.611 to provide filaments having atenacity of 4.88 grns./ denier, an initial modulus of 82 gins/denier andan ultimate elongation of 19.4%. After cold-drawing, the filaments wereobserved to contract 70% and had a crimp frequency of 12 crimps per inchin a tension-free state.

In light of the foregoing, it may now be appreciated that there has beenherewith disclosed a novel and beneficial apparatus for use in theproduction of filaments possessing a self-crimping potential, whichapparatus involves only simple and easily accomplished modifications ofotherwise conventional spinning equipment. By use of such apparatus thetechnique of converging two or more streams at a differential linearvelocity through a common orifice and taking off the resulting filamentat a linear velocity greater than any constituent stream velocity isexpeditiously facilitated. As will readily be understood, numerousvariations and modifications may occur to those skilled in the artappertaining hereto in light of the above teachings. It is, therefore,:to be understood that, within the scope of the appended claims, theinvention may be practiced otherwise and as specifically describedherein.

What is claimed is:

1. A spinning device for use in the production of selfcrimpingthermoplastic filaments comprising a source of filament-formingmaterial, a spinnerette plate having at least two converging passagewaysextending therethrough to merge at a point substantially coincident witha face thereof to define an extrusion orifice supplied by each of saidpassageways, said passageways being connected to said source and beingof different cross-sectional areas at least in the vicinity of saidorifice, whereby said filament-forming medium passing from said sourcethrough the smaller of said passageways is caused to issue at a greaterlinear velocity relative to that issuing of said other passageways toprovide a filamentary stream having asymmetrically distributeddilferential in linear velocity over its cross-section.

2. The device of claim 1 wherein those passageways supplying a givenorifice are characterized by a substantial equality in mass flowresistance, whereby a filamentary stream issuing from said orificeexhibits a substantial equality of flow contribution from each of saidpassageways, as measured over the stream cross section.

3. The device of claim 1 wherein the pressure drop between a source offiber-forming medium and an orifice through one of said passageways issubstantially equal to that through the other of said passageways,whereby a filamentary stream issuing from said orifice exhibits asubstantial equality of flow contribution from each of said passageways,as measured over the stream cross section.

References Cited UNITED STATES PATENTS 2,149,425 3 1939 Draemann.3,014,237 12/ 1961 Breen. 3,117,906 1/ 1964 Tanner.

3,161,914 12/1964 Bloomfield et al. 188 3,192,563 7/1965 Crompton 1'8-8FOREIGN PATENTS 536,574 1931 Germany. 970,844 1964 Great Britain.

WILLIAM J. STEPHENSON, Primary Examiner.

